Multiple interferer cancellation for communications systems

ABSTRACT

An interference cancellation system (ICS) may be used with a communication system to prevent or minimize interference from one or more sources. The ICS may receive radio RF signals comprised of one or more signals of interest (SOI) and multiple interfering signals. The ICS may use a sample of the interfering signals to cancel the interfering signals from the SOI. The multiple interfering signals may be converted into a single optical signal for cancellation. One or more optical cancellation paths may be used for interference cancellation. Each optical cancellation path may include an optical attenuator and/or an optical delay to achieve phase shifts and/or delays for interference cancellation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/649,856 filed on May 21, 2012, U.S. ProvisionalPatent Application No. 61/649,715, filed May 21, 2012, and U.S.Provisional Patent Application No. 61/649,843, filed May 21, 2012, thecontents of which are incorporated by reference herein in theirentirety.

This application may include subject matter that is related to subjectmatter included in U.S. Patent Application No. [Attorney Docket No.LTEL_ICS_US01], filed May 21, 2013 and U.S. Patent Application No.[Attorney Docket No. LTEL_RI_US01], filed May 21, 2013.

BACKGROUND

The radio spectrum is crowded due to the growth in the demand for radiofrequency (RF) applications. Multiple wireless communications systemsmay be allocated in close proximity or in the same radio spectrum. Forexample, one or more RF jammers or other wireless communications systemsmay be in close proximity to, and cause interference at a transceiverattempting to receive a signal from one or more other communicationssystems. Acceptable quality of performance of a radio transceiver and/orradio communications may be difficult to achieve due to suchinterference.

SUMMARY

Systems and methods are described herein for an interferencecancellation system (ICS) that may be used with various communicationssystems to prevent or minimize interference from one or more sources.For example, the ICS may be configured to receive RF signals comprisedof at least one signal of interest (SOI) and a plurality of interferingsignals. The ICS may determine a sample of the interfering signals andconvert the RF signals to optical signals for cancellation of theinterference. The plurality of interfering signals may be converted intoa single optical signal for cancellation. Optical attenuators and ordelays may be used by the ICS for weighted networks to achieveamplitude, phase shifts, and delays for signal cancellation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system diagram of an example architecture in which aninterference cancellation system (ICS) may be implemented.

FIG. 2 is a system diagram of an example interference cancellationsystem.

FIG. 3A illustrates an example system architecture for an ICS.

FIG. 3B illustrates an example architecture of an Optical Subsystem ofan ICS.

FIG. 3C illustrates an example architecture of an RF Subsystem of anICS.

FIG. 3D illustrates an example architecture of a Digital Subsystem of anICS

FIG. 4 is a diagram that depicts an example architecture that may beimplemented for cancelling interference from multiple interferers.

FIG. 5 is a diagram that depicts another example of an ICS forcancelling interference from multiple interferers.

FIG. 6 is a graph that depicts an example signal before and aftercancellation of interference fom multiple interferers.

FIG. 7 is a graph that depicts another example signal before and aftercancellation of interference from multiple interferers.

DETAILED DESCRIPTION

An interference cancellation system (ICS) may be used with variouscommunications systems to prevent or minimize interference with voiceand/or data transmitted via the communications systems. For example, theICS may be used to enable receipt of wireless communications by atransceiver in proximity to other wireless communications that may becausing interference, such as a radio frequency (RF) jammer or othercommunications device that may cause RF interference.

RF jamming may be used as a defense to protect military vehicles frommines and/or Improvised Explosive Devices (IEDs), such as thosedetonated remotely for example. RF jamming may be used to disrupt enemycommunications. To effectively jam hostile communications channels, thejammers may transmit high power, broad-band signals in the same bandsthat may be used for friendly communications. While providing protectionby blocking enemy signals, jammers may saturate the electromagneticspectrum and interfere with friendly signals being transmitted orreceived within a wireless range of the jammers. Embodiments aredescribed herein that enable compatibility between jammers/interferersand other communications equipment. While the embodiments describedherein may be described with reference to jammers and/or other militarycommunications equipment, they may be implemented in any communicationsystem to minimize or cancel interference at a transceiver.

Communications equipment and jammers may work in harmony even when thesystems are operating at the same frequency. An ICS may be seamlesslyintegrated with existing field equipment (e.g., jammers/interferersand/or radio transceivers) for communication system deployment in thefield, in the air, on ships, on submarines, or in any other area inwhich wireless communications equipment may be implemented. The ICS maybe used to enable the communications equipment to transmit and/orreceive information via one or more wireless signals while a jammer maycause interference. The ICS may cancel the interfering signals andallowing the data being transmitted to be properly received.

An optical ICS that may receive one or more signals of interest (SOIs)and one or more interfering signals and may perform cancellation of theinterfering signals to allow the SOI to be properly communicated. Theoptical ICS may connect to communications equipment and/or jammers,which may be in service. The optical ICS may identify remotejammers/interferers to reduce jammers/interference, such asjamming/interference that may not be removed by receiver RF front endfillers for example. The optical ICS may be packaged into a stand-aloneICS box or incorporated into the communications equipment. For example,the optical ICS may be integrated with the jammer and/or the deviceintended to receive the SOI. If the ICS is integrated with a radioand/or jammer, the ICS may be integrated with the co-located radioand/or jammer without modification to these systems or degradation totheir system performance.

The ICS may be implemented in the field, in the air, on ships, onsubmarines, or in any other area in which wireless communicationsequipment may be implemented. For example, the ICS may be implemented ona Navy ship or submarine and may be compatible with the Navy's multipleforms of communications equipment. The ICS may be used by Blue Forceunits to simultaneously conduct missions while maintaining othercommunications, command, and control. This combination may enablesituational awareness by the warfighters, even in the environment wheremultiple radio transceivers are co-located. The ICS may be us6ed bycellular communications devices, satellite communications (Satcom)devices, or any other RF communications device.

The ICS may interface to any tactical radio transceiver and/or may beimplemented as an upgrade kit. For example, the ICS may be kitted withmounting hardware and/or cable sets to match various communicationsequipment configurations. The ICS may be implemented as a plug and playsystem. The ICS design may be integrated with any radio transceiverand/or communications equipmemt without modification to the radiotransceiver andur communications equipment. This may allow easyinstallation of the equipment as a retro upgrade, such as on a ship orsubmarine for example.

The presence of multiple communications systems in the same or similararea (e.g., in the field, in the air, on a ship, or on a submarine) maycreate an inter-jamming environment for one or more transceivers in thatarea. The ICS may be used for the removal of interference from multipleinterferers. This may allow various co-located radio transceivers tocommunicate seamlessly with other communications systems within and/oroutside the perimeter of a given area. Technical metrics considered forenabling performance may include operating bandwidth, cancellationbandwidth, cancellation level, and/or bit error rate for communicationequipment.

The embodiments described herein may be used to provide an automated RFspectrum management and multiple interference cancellation forcommunications systems. Narrowband interference of a wideband signal,wideband interference, and or co-site interference may be considered indetermining efficient use of the frequency spectrum. The describedembodiments may be implemented using hardware and/or software.

FIG. 1 illustrates an example system including an ICS. For example, ICS102 may be configured to provide interference cancellation inmulti-faceted environments, such as environments including one or moreremote interferers (e.g., an interferer is not co-located and/or is notcoupled to the ICS) and/or one or more unknown jammers/interferers. Asillustrated in FIG. 1, Local Radio 104 may be attempting to communicatewith Remote Radio 106. Each of the radios may include a transceiverconfigured to provide operable wireless communications between the radiosystems. For example, Local Radio 104 may include a local transceiverthat is configured to perform transmit and/or receive processing ofradio signals transmitted from and/or received by Local Radio 104. Thelocal transceiver may be coupled to one or more antennas in order totransmit and/or receive radio signal over the air. Similarly, RemoteRadio 106 may also include a transceiver (e.g., remote transceiver) thatis configured to perform transmit and/or receive processing of radiosignals transmitted from and/or received by Remote Radio 106. The remotetransceiver may be coupled to one or more antennas in order to transmitand/or receive radio signals over the air.

As an example, Remote Radio 106 may transmit a signal of interest (SOI)to Local Radio 104. For example, Remote Radio 106 may send acommunication from an ally that is meant to be received by the user ofLocal Radio 104. The distance between the location of Remote Radio 106and Local Radio 104 may be expressed as D_(RS). The received signalpower of the SOI may be expressed as P_(SOI).

However, during the period wherein Remote Radio 106 is attempting tocommunicate with Local Radio 104, one or more interference signals maybe emitted by various interference sources. The interference signals maybe received at Local Radio 104 in addition to the SOI. For example,Jammer 108 may include a transmitter and one or more antennas that maybe configured to transmit an Interferer Signal (I). The InterfererSignal (I) may include transmissions on one or more frequencies that maybe the same or close to one or more frequencies that may be used totransmit the SOI, and hence may result in interference between the SOIand the I. The presence of the Interferer Signal may make it difficultfor the local transceiver of Local Radio 104 to properly receive andprocess the SOI. The distance between the location of Jammer 108 andLocal Radio 104 may be expressed as D_(RTI). The received signal powerof the Interferer Signal at Local Radio 104 may be expressed asP_(TXTI).

In many practical scenarios, the Interferer Signal (I) may be a muchhigher power signal than the SOI in the vicinity of Local Radio 104. Forexample, Local Radio 104 may be co-located with Jammer 108 on a militaryvehicle. Remote Radio 106 may be several miles away from both LocalRadio 104 and Jammer 108. Thus, for one or more example it may beassumed that D_(SOI) is much larger (e.g., orders of magnitude larger)than D_(RTI). Additionally, since Jammer 108 typically emits a very highpower Interferer Signal that does not travel very far to reach LocalRadio 104 (e.g., while Remote Radio 106 may emit a relatively lowerpower SOI that may travel orders of magnitude farther than theInterferer Signal (I) prior to reaching Local Radio 104), it may also beassumed that P_(TXTI) is much larger (e.g., order of magnitude larger)than P_(SOI). This may be the case when the Jammer is located in oraround the vicinity of the ICS, while Remote Radio 2 may be severalmiles (or more) away from the ICS.

Thus, when both Remote Radio 106 and Jammer 108 are in simultaneousoperation, the actual signal received at the one or more antennasassociated with Local Radio 104 may be a combined SOI and InterfererSignal (e.g., SOI+I). It may be difficult for Local Radio 104 todetermine the SOI from the SOI+I signal using conventional interferencemitigation techniques, for example since the I signal may be much higherpower than the SOI and may include one or more components in the samefrequency range as the SOI.

Therefore, in an example, ICS 102 may be inserted between the one ormore antennas associated with Local Radio 104 and the local transceiverof Local Radio 104. ICS 102 may be configured to attempt to cancel theInterferer Signal (I) from the combined SOI+I signal that is received atthe one or more antennas associated with Local Radio 104. For example,ICS 102 may obtain a sample of the Interferer Signal (I), for examplevia Coupler 110 that is operably connected to Jammer 108. For example,in the case where both Jammer 108 and Local Radio 104 arc co located ona military vehicle, Coupler 110 may act to provide ICS 102 with a sampleof the Interferer Signal (I) produced by Jammer 108 prior to theInterferer Signal (I) being sent over the air using one or more antennasassociated with Jammer 108 (e.g., Coupler 110 may be inserted betweenthe transmitter of Jammer 108 and the one or more antennas associatedwith Jammer 108). Coupler 110 may be configured to provide a physicalcable connection such that ICS 102 may receive a copy of the RF signalbeing transmitted by Jammer 108. In another example, the InterfererSignal (I) may be communicated to the ICS via a wireless signal. Thesample of the Interferer Signal (I) that is provided to the ICS may beexpressed as I_(cp).

In order to properly detect the SOI from the SOI+I signal, ICS 102 maybe configured to use one or more of RF, optical, and/or digital signalprocessing (DSP) techniques to cancel the Interferer Signal (I) from theSOI+I signal. For example, the ICS may include an RF Subsystem, anOptical Subsystem, and/or a Digital Subsystem. The RF Subsystem, theOptical Subsystem, and/or the Digital Subsystem may be configured toremove or cancel most or all of the Interferer Signal (I) from thesignal received over the one or more antennas associated with LocalRadio 104. The techniques utilized by the RF Subsystem, the OpticalSubsystem, and/or Digital Subsystem 380 are described in more detailbelow. Upon successfully cancelling the Interferer Signal (I), ICS 102may send the SOI to the local transceiver of Radio 104 for furtherreception processing.

For example, ICS 102 may include one or more of optical components(e.g., an Optical Subsystem), radio frequency components (e.g., an RFSubsystem), and/or digital signal processing components (e.g., a DigitalControl Subsystem) to perform interference cancellation. In an example,ICS 102 may convert RF and/or microwave input signals into opticalsignals. The ICS may use optical components to perform preciseattenuation and time delay of the converted signal to achieve optimalcancellation depths across an instantaneous bandwidth of hundreds ofMHz. For example, the system may operate to perform interferencecancellation from high frequency (HF) bands (e.g., 3-30 MHz) to S bands(e.g., 2 to 4 GHz) and beyond.

The optical components of ICS 102 may be configured to perform preciseinversion and recombination of two RF signals, which may be achievedwith greater accuracy in the optical domain than in the RF domain. Forthe undesired interference signal to be perfectly or near-perfectlycancelled, the inversion process may result in an inverted interferencesignal that is nearly an exact replica of the original signal, exceptfor the relative inversion. In the RF domain, it is difficult to achievenear-perfect replication of a signal over a wide range of frequencies.However, optical components may be configured to achieve near perfectreplication and inversion during an inversion and recombination process.

FIG. 2 illustrates an example ICS 200. For example, ICS 200 may includeone or more of RF Subsystem 202, Optical Subsystem 204, and/or DigitalSubsystem 206. RF Subsystem 202 may be operably coupled to one or moreantennas 210. One or more antennas 210 may be used by Radio 208 fortransmitting and/or receiving signals from remote radios. For example, asignal of interest (SOI) plus the Interferer Signal (I) (e.g., SOI+I)may be received via one or more antennas 210 and provided to ICS 200(e.g., RF Subsystem 202). RF Subsystem 202 may also receive a copy ofthe Interferer Signal (I) as an input in addition to the combined SOI+Isignal received via the one or more antennas 210. For example, ICS 200may be operably coupled to a jammer that produces the Interferer Signal(I), and the output of the jammer may be provided to ICS 200 via aphysical connection (e.g., via a coupler of FIG. 1).

In an example, ICS 200 may receive the Interferer Signal via a secondantenna and/or a plurality of second antennas (not shown in FIG. 2). Oneor more of RF subsystem 202 andor Digital Subsystem 206 may beconfigured to determine an estimate of the Interferer Signal (I) basedon a signal received via one or more one or more antennas 201 and/or thesecond antenna and/or the plurality of second antennas. The estimate offthe interferer signal may then be utilized by the ICS. One or more of RFSubsystem 202, Optical Subsystem 204, and/or Digital Subsystem 206 maybe configured to utilize knowledge of the Interferer Signal (I) tocancel Interferer Signal from the combined SOI+I signal received via theone or more antennas 210. The result of the cancellation may be the SOI.RF Subsystem 202 may send the SOI to Radio 208 that is operably coupledto the RF subsystem for further reception processing (e.g.,demodulation, decoding, etc).

As an example, many common types of jammers are configured to saturatereceivers operating at or near 300 MHz. For example, such jammers may bedesigned to prevent communications that utilize frequencies in or around300 MHz (e.g., garage door openers). Typical broadband, noise-likejammers in this range may output signals with power levels ofapproximately 100 W (50 dBm) over a 300 MHz to 400 MHz bandwidth.However, such a jammer may prevent communication over a large portion ofthe 225 MHz to 512 MHz UHF communications band as well as a majorportion of the 292 MHz to 318 MHz UHF Satellite Communication (SATCOM)band, in addition to the desired 300 MHz cancellation. The +50 dBm 100MHz broadband noise may be equivalent to a 15 dBm noise signal over aplurality of 25 kHz communications channels. Assuming 20 dB of antennacoupling loss between a jammer and ICS 200, the jamming signal (e.g.,Interferer Signal (I) reaching the radio transceiver antenna may beexpected to be around −5 dBm over the 25 kHz channel. For example, 20 dBantenna coupling estimate for 300 MHz operation may be estimated usingtwo quarter wave monopoles separated by three wavelengths over a perfectground plane. This level of interference may be more than sufficient tojam communications in this band, assuming transceiver sensitivitybetween −110 dBm and −120 dBm for 10 dB signal-to-noise and distortionratio (SINAD), depending on the operating mode and application.

Optical cancellation techniques may offer broadband interferencecancellation with a significantly greater depth than conventional RFcancellation. Optical Subsystem 204 may be configured to performinterference cancellation using optical interference cancellationtechniques. For example, for a 100 MHz broadband jamming signal, over 30dB of interference cancellation may be obtained using opticaltechniques. Optical cancellation is typically more effective than RFcancellation alone, for example due to the higher bandwidth of operationand much lower amplitude and/or frequency dispersion in opticalcomponents as compared to RF components. An optical link between areceived and sampled jammer output (e.g., the sampled jammer signal) andICS 200 may reduce directly coupled jammer power, preventing the jammersignal from reaching the transceiver antenna input. Optical cancellationdoes not suffer from RF leakage into an RF interference cancellationsystem, which may create offsets that reduce effective jammercancellation in the ICS.

By cancelling the majority of the interferer signal in the opticaldomain, ICS 200 may allow communication systems to perform simultaneousjamming and operative communication in the jammed frequency range. Thisoptical cancellation technique may utilize active cancellation betweenjammers (e.g., counter-IED jammers) and radio systems to preventself-interference. The ICS may also be applied to commercial systemssuffering from saturated receivers. Optical interference cancellationmay allow for processing an extremely wide range of frequencies withminimum distortion. The optical components may allow for multiple ordersof magnitude in bandwidth, as well as lower amplitude and phasefluctuation.

For an active interference implementation, the interfering signal may beaccurately estimated or sampled in real time. A copy of the cleantransmit signal from any jammer or interferer may be obtained usingdirect coupling or magnetic coupling with an electromagneticinterference (EMI) probe and/or current probe. In the case of a remotejammer (e.g., the jammer is not directly or physically connected to theICS), a copy of the jamming signal may be obtained by accuratelyestimating the jammer signal using a signal received via an antenna.

FIG. 3A illustrates an example system architecture for an ICS. Forexample, an ICS may include one or more of RF Subsystem 310, OpticalSubsystem 350, and/or Digital Subsystem 380. Power Supply 304 mayprovide power to one or more of RF Subsystem 310, Optical Subsystem 350,and/or Digital Subsystem 380. As shown in FIG. 3A, Jammer 302 may beoperably coupled to RF Subsystem 310. RF Subsystem 310 may include oneor more RF processing components, and the components and functionalityof RF Subsystem 310 are described in more detail with respect to FIG.3C. Additionally, Jammer 302 may be operably coupled to one or moreantennas e.g., Antenna1 304). Jammer 302 may be coupled to the one ormore antennas (e.g., Antenna1 304) via RF Subsystem 310. For example, ajammer coupler with RF Subsystem 310 may be used so that the ICS may bequickly inserted between an operational jammer and an antenna used totransmit the jammer signal. P_JMR may represent the jammer signal priorto being transmitted by the one or more antennas (e.g., Antenna1 304).RF_JMR may represent the RF jammer signal transmitted via the one ormore antennas (e.g., Antenna1 304).

In the example shown in FIG. 3A, Jammer 302 may be physically connectedto RF Subsystem 310 in order for RF Subsystem 310 to obtain a sample orcopy of the jammer signal. A copy of the transmitted Jammer signal(e.g., RF_JMR) may be used as an input to the interference cancellationsystem. For example, one or more components of RF Subsystem 310 (e.g.,Jammer RF Front-End processing component(s). Jammer Detector components,etc.) may perform RF processing on the sample-copy of the jammer signal(e.g., RF_JMR) in order to filter the jammer signal and/or detect jammeroperation prior to processing by Optical Subsystem 350. Such Jammersignal pre-processing will be described in more detail with respect toFIG. 3C.

When Jammer 302 is in use, jammer detection component(s) of RF Subsystem310 may send an indication that Jammer 302 is in operation to DigitalSubsystem 380 via the JMR_ON signal. The ICS may be configured todetermine to begin interference cancellation based on the concurrentdetection of Jammer 302 transmission and lack of transmission by RadioTransceiver 308. For example, Radio Transceiver 308 may be any radiosystem that may experience interference due to transmissions from Jammer302. Radio Transceiver 308 may be configured to perform receive and/ortransmit processing of RF signals transmitted via one or more antennas(e.g., Antenna2 306). To prevent interference from Jammer 302 fromsaturating Radio Transceiver 308 during periods where it is attemptingto receive an SOI via Antenna2 306, an ICS may be inserted between RadioTransceiver 308 and Antenna2 306. The ICS may receive a signal comprisedof the combination of the SOI and the Interferer Signal (I) (e.g.,SOI+RF_JMR) via Antenna2 306 and may remove a large majority of theInterferer Signal (I) (e.g., RF_JMR) such that the SOI may be passed toRadio Transceiver 308 for further processing.

After performing RF preprocessing on the sampled jammer signal (e.g.,RF_JMR), RF Subsystem 310 may send a copy of the Jammer signal toOptical Subsystem 350 in order for Optical Subsystem 350 to performcancellation of the jammer signal from the signal that is received viaAntenna2 306. For example, RF_in1 may represent the copy of the jammersignal (e.g., RF_JMR) provided to Optical Subsystem 350. Operation ofOptical Subsystem 350 will be described in more detail with respect toFIG. 3B.

In an example, Antenna2 306 may be configured to receive a signal ofinterest from a remote radio (e.g., SOI). While Jammer 302 is inoperation, the jammer signal (e.g., RF_JMR) may interfere with SOI suchthat Antenna2 306 receives the signal SOI+RF_JMR. RF Subsystem 310 mayperform RF preprocessing on the signal received via Antenna2 306 (e.g.,SOI+RF_JMR) prior to sending the combined jammer and SOI signal toOptical System 350 for interference cancellation. For example, RFSubsystem 310 may be configured to perform some initial cancellation ofthe jammer signal (e.g., RF_JMR) from the combined jammer and SOI signal(e.g., SOI+RF_JMR) prior to sending the signal to Optical Subsystem 350.RF Subsystem 310 may also perform other signal processing and filteringon the combined jammer and SOI signal (e.g., SOI+RF_JMR) as is describedwith respect to FIG. 3C prior to sending the combined jammer and SOIsignal (e.g., SOI+RF_JMR) to Optical Subsystem 350. The signalrepresenting the combined jammer and SOI signal (e.g., SOI+RF_JMR) sentfrom RF Subsystem 330 to Optical Subsystem 350 may be represented asRF_in2.

Optical Subsystem 350 may receive a copy of the (e.g., pre-processed)jammer signal (e.g., RF_in1) and a copy of the (e.g., pre-processed)combined jammer and SOI signal (e.g., RF_in which may correspond to thecombined jammer plus SOI signal—SOI+RF_JMR) from RF Subsystem 310.Optical Subsystem 350 may be configured to cancel most or all of theinterferer signal (e.g., RF_in1) from the combined jammer and SOI signal(e.g., RF_in2). The optical interference cancellation process may bedescribed in more detail with respect to FIG. 3B. Generally, each of theinterferer signal (e.g., RF_in1) and the combined jammer and SOI signal(e.g., RF_in2) may be converted from the RF domain to the opticaldomain. One of the two signals (e.g., RF_in1 or RF_in2) may be invertedduring the optical conversion process. One or more optical paths (e.g.,an optical path may include one or more optical attenuators and one ormore optical delay lines) may be used to attenuate and/or delay theoptically converted jammer signal. Optical Subsystem 350 may becontrolled by Digital Subsystem 380 to variably attenuate and/or delaythe optical version of the jammer signal to achieve maximumcancellation. Digital Subsystem 380 may control the variable attenuationand or variable delays applied by Optical Subsystem 350 based on theoutput of Optical Subsystem 350 and processing performed by RF Subsystem310.

The variably attenuated and variably delayed optical version of thejammer signal may then be combined with the optically converted combinedjammer and SOI signal. One of the variably attenuated and variablydelayed optical version of the jammer signal and the optically convertedcombined jammer and SOI signal may be inverted prior to being combinedby Optical Subsystem 350. The resultant signal may be an optical versionof the SOI (or nearly so), provided that correct attenuation and/ordelays were applied to the optical jammer system. The optical version ofthe SOI may then be converted back to the RF domain and output byOptical Subsystem 350 for further processing by RF Subsystem 310. RFSubsystem 310 may perform further processing on the output of OpticalSubsystem 350 in order to provide additional information that may beused by Digital Subsystem 380 for controlling Optical Subsystem 350. TheRF version of the SOI signal may then be sent from RF Subsystem 310 toRadio Transceiver 308.

FIG. 3B illustrates an example architecture of Optical Subsystem 350.The RF jammer signal (e.g., RF_in1) may be received from RF Subs6ystem310 via Laser Modulator1 352. The terms laser modulator, opticalmodulator, and/or optical transmitter module may be used interchangeablyherein. For example, Laser Modulator1 352 may be a laser modulator thatperforms a −180 degree optical phase shift on the jammer signal (e.g.,RF_in1) during the RF-to-optical conversion process. The result of the−180 phase shift to the jammer signal during RF-to-optical conversionmay be referred to herein as the optically inverted jammer signal. TheRF-to-optical conversion may be realized using one or more lasermodulators. In an example, the optical transmitters/laser modulators mayutilize a counter phase Mach-Zehnder modulator (MZM) in order to convertthe RF signal to optical signals. In another example, the opticaltransmitters/laser modulators may utilize direct modulation from RF tooptical as described herein. Laser Modulator1 352 may provide RFamplitude and phase tracking, minimal DC offset, and/or reduceddistortion at the Photodiode Detector output (e.g., output of PhotodiodeDetector 372). The phase shifter (e.g., −180 phase shift) may beimplemented as part of Laser Modulator1 352 and/or may be a separatecomponent.

The optically inverted jammer signal output from Laser Modulator1 352may be sent to Splitter 354. For example, the optically inverted jammersignal may be split into a plurality of separate optical processingpaths for further processing. Each optical processing path may beindividually attenuated and/or individually delayed. For example, afirst optical processing path from Splitter 354 may include VariableAttenuator1 356 and/or Variable Delay Line1 358. The variableattenuation and variable delay utilizedd by the optical processing pathsof Optical Subsystem 350 are described in more detail below. Controlsignals that control the operation of the components of the firstoptical processing path (e.g., Variable Attenuator1 356 and/or VariableDelay Line1 358) may be provided by Digital Subsystem 380. For example,a_c1 may be a control signal from Digital Subsystem 380 that controlsthe amount by which Variable Attenuator1 356 attenuates the opticallyinverted jammer signal sent from Splitter 354 over the first opticalprocessing path. Similarly, t_c1 may be a control signal from DigitalSubsystem 380 that controls the amount by which Variable Delay Line1 358delays the optically inverted jammer signal sent from Splitter 354 overthe first optical processing path. The amount of attenuation and/or theamount of time delay may be controlled in order to achieve a desired ormaximum amount of interference cancellation.

As may be appreciated, embodiments contemplate that the opticallyinverted jammer signal may be split by Splitter 354 into any number ofseparate optical processing paths for attenuation and delay based on thedesired level of cancellation and operating environment. For example,each optical processing path (e.g., an optical attenuator and/or anassociated optical delay line) may be used to cancel a differentinterference signal(s) and/or different components of an interferingsignal. For example, a first optical processing path may be configuredto cancel the direct line interferer signal. A second optical processingpath may be configured to cancel a first multipath propagation of theinterferer signal. An Nth (e.g., where N may be an integer) opticalprocessing path may be configured to cancel an Nth multipath propagationof the interferer signal, etc. In an example, each optical processingpath may be configured to cancel a different interferer. The opticalattenuation weight and/or the optical delay line weight of each of theoptical processing paths may be different depending on the type ofcancellation desired.

Each optical processing path may be associated with different controlsignals from Digital Subsystem 380. For example, a second opticalprocessing path may include Variable Attenuator2 360 and/or VariableDelay Line2 362. An Nth optical processing path may include VariableAttenuatorN 364 and/or Variable Delay LineN 366. Digital Subsystem 380may control the operation of the components of each of the opticalprocessing paths to achieve a desired level of interferencecancellation. For example, Variable Attenuator1 356 may be controlledwith signal a_c1. Variable Attenuator2 360 may be controlled with signala_c2, and/or Variable AttenuatorN 364 may be controlled with signala_cN. Similarly, Variable Delay Line1 358 may be controlled with signalt_c1, Variable Delay Line2 362 may be controlled with signal t_c2,and/or Variable Delay LineN 366 may be controlled with signal t_cN.

Power may be provided to the components of Optical Subsystem 350 byPower Supply 304. In an example, the power may be routed to thecomponents of Optical Subsystem 350 from RF Subsystem 310 and/or fromDigital Subsystem 380. In an example, there may be a direct connectionfrom Power Supply 304 to Optical Subsystem 350. The power signal forVariable Attenuater1 356 may be signal a_v1, the power signal forVariable Attenuator2 360 may be signal a_v2, and the power signal forVariable AttenuatorN 364 may be signal a_vN. The power signal forVariable Delay Line1 358 may be signal t_v1, the power signal forVariable Delay Line2 362 may be signal t_v2, and the power signal forVariable Delay LineN 366 may be signal t_vN. Power Supply 304 may alsosupply power to one or more other components of Optical Subsystem 350,for example one or more of Laser Modulator1 352, Splitter 354, Combiner368, Laser Modulator2 370, Photodiode Detector 372, and/or the like.

In an example, the optically inverted jammer signal may be processed byone or more optical processing paths prior to being combined with anoptically converted version of the combined jammer and SOI signal. Forexample, the combined jammer+SOI signal (e.g., RF_in2) may be convertedfrom RF to the optical domain by Laser Modulator2 370. Laser Modulator1352 and Laser Modulator2 370 may be two matched laser modulators suchthat coherent optical cancellation may be performed. For example, LaserModulator1 352 may be configured to invert the jammer signal during theRF-to-optical conversion process such that the optically inverted jammersignal may be combined optically with the optically converted combinedjammer and SOI signal to result in cancellation of the RF_JMR signalsuch that the SOI signal can be isolated. An optical signal that isoptically phase shifted by −180 degrees that is combined with anunshifted version of the same optical signal may result in completedestructive interference/complete cancellation if the phase shift isideal. Phase shifting in the optical domain may achieve near idealresults across a wide frequency range.

Thus, after the optically inverted jammer signal is processed by thevariable attenuator(s) and/or variable delay line(s), for example toproperly scale and time-align the optically inverted jammer signal withthe optically converted combined jammer and SOI signal, the output ofthe optical processing lines may be combined with the opticallyconverted combined jammer and SOI signal at Combiner 368. If values forvariable attenuation and/or variable delays were properly selected, thecombining of the optical signals should result in the cancellation ofthe jammer signal from the combined jammer and SOI signal. This opticalversion of the SOI signal may be sent to Photodiode Detector 372 forfurther processing and conversion back to the RF domain. The SOI signal(e.g., Op_out) may then be sent back to RF Subsystem 310 for furtherprocessing. For example, signal Op_out may be tested to determinewhether a desired level of interference cancellation has been achieved.An RF Correlator/Detector 338 (e.g., FIG. 3C) may be used to determinethe level of interference cancellation, for example by associating therelative power level of the Op_out signal with the level of interferencecancellation. Digital Subsystem 380 may determine whether the signaloutput from the optical subsystem representing the SOI signal (e.g.,Op_out) meets a threshold signal-to-noise (SNR) level. For example, ifthe Digital Subsystem determines that the SNR of the Op_out signal is 10dB or greater, then it may be determined that the interference from thejammer has been sufficiently cancelled and the resultant SOI signal(e.g., Op_out) may be sent to the radio Transceiver 308 (e.g., FIG. 3A).

FIG. 3C is an example system diagram of RF processing components thatmay be included in RF Subsystem 310. For example, an interferer signalmay be sent from Jammer 302 to Jammer Coupler 312. Jammer Coupler 312may split the interferer signal from Jammer Coupler 312 such that thesignal may be transmitted via the jammer antenna and a sample or copy ofthe signal may be used for interference cancellation by the ICS. JammerCoupler 312 may provide an accurate sample of the jammer signal to theJammer RF Front-End Processing components. Jammer Coupler 312 may be anRF coupler, for example with a coupling factor in the range of 20 to 50dB depending on the jammer output power. In an example, a sample of thejammer signal may be obtained using a current probe that is operablycoupled to the jammer antenna.

Jammer Coupler 312 may send a sample of the jammer signal to betransmitted over the jammer antennas to one or more jammer RF front-endprocessing components. Example RF front-end processing components mayinclude one or more of variable attenuators), a low noise amplifier(s),RF bandpass filter(s), coupler(s), isolator(s) and/or tunable RFfilter(s). The jammer RF front-end components may be configured tofilter the jammer signal prior to processing by the Optical Subsystem.For example, Jammer RF Front End may be configured to prevent thegeneration of additional harmonics and/or intermods of the jammer signalwithin the ICS.

For example, as illustrated, in FIG. 3C, a copy of the jammer signal maybe received at Isolator1 314 of the jammer RF front-end. Isolator1 314may be a passive device that may be used to prevent jammer and/or otherRF signals from being affected by excessive signal reflection from theRF processing components and/or to control the direction of signal flowin the RF subsystem. Isolator1 314 may pass a copy of the jammer signalto Coupler1 316. Coupler1 316 may be configured to send a copy of thejammer signal to Jammer Detector 344. Jammer Detector 344 may beconfigured to detect when the jammer is in operation. For example, whenthe jammer is in use, Jammer Detector 344 may indicate to DigitalSubsystem 380 that the jammer is on using signal JMR_ON. The ICS (e.g.,Digital Subsystem 380) may be configured to determine to begininterference cancellation based on the concurrent detection of Jammertransmission (e.g,. based on JMR_ON) and lack of transmission by RadioTransceiver 308.

Jammer Detector 344 may be configured to automatically detect when theJammer begins transmission. For example, Jammer Detector 344 may includean RF Power Detector (e.g., RF Power Detector1) and/or a comparator(e.g., Comparator1). The comparator may be used to set the thresholdpower level used to determine whether Jammer 302 is currentlytransmitting-operating. The comparator may be an RF component thatcompares two voltages and/or two currents and outputs an indication ofwhich of the two inputs are larger. For example, the comparator may seta power level threshold, above which it is assumed Jammer 302 is inoperation, below which it is assumed that Jammer 302 is not inoperation. RF Power Detector1 of Jammer Detector 344 may be configuredto detect the jammer signal and/or the power level of the jammer signaland send an indication of the power level to comparator1 of JammerDetector 344. The comparator1 may be configured to compare the receivedpower level to a power level threshold. For example, the power levelthreshold may be +24 dBm, although the power level may vary depending onthe configuration and properties of Jammer 302. If the received powerlevel exceeds the power level threshold, then Comparator1 of JammerDetector 344 may send an indication that Jammer 302 is currentlytransmitting to Digital Subsystem 380, for example via the JMR_ONsignal. If the received power level does not exceed the power levelthreshold, then Comparator1 of Jammer Detector 344 may send anindication that Jammer 302 is not currently transmitting (e.g., isturned off) to Digital Subsystem 380, for example via the JMR_ON signal.

One or more jammer RF front-end components may be configured to performinitial interference cancellation processing on the jammer signal priorto further interference cancellation processing in Optical Subsystem350. For example, RF Variable Attenuator1 318 may be a variable RFattenuator that is controlled by Digital Subsystem 380. For example,control signal CTRL_AT1 may be used by Digital Subsystem 380 to controlRF Variable Attenuator 318 (e.g., not shown in FIG. 3C). By varying theattenuation level of RF Variable Attenuator1 318 prior to sending thejammer signal to Optical Subsystem 350, Digital Subsystem 380 mayselectively perform initial interference cancellation processing in theRF domain prior to further processing in the optical domain. Control ofRF Variable Attenuator 318 by Digital Subsystem 380 (e.g., usingCTRL_AT1) may be based on feedback received by Digital Subsystem 380from one or more of RF Correlator/Detector 338, RF FrequencyDetectorRSSI 340, and/or Transmit Power Level Detector 342. The variablyattenuated RF jammer signal may then be sent to RF Filter1 320. RFFilter1 320 may include one or more of a fixed RF filter and/or avariable RF filter for processing the jammer signal. RF Filter1 320 maysend the preprocessed jammer signal (e.g., RF_in1) to optical subsystem350 for further interference cancellation processing.

Transmit/Receive Switch1 346 may be operably coupled to Antenna2 306 andmay send SOI+RF_JMR to the Receive RF Front-End component of the RFSubsystem. The Receive RF Front-End components may include one or morevariable/tunable attenuators), low noise amplifiers) (LNAs), fixed RFfilter(s), and/or variable RF filter(s). For example, LNA1 322 mayamplify the signal received via Antenna2 306 and send the amplifiedsignal to Rf Variable Attenuator2 342. RF Variable Attenuator2 342 maybe a controllable/tunable attenuator that is controlled by DigitalSubsystem 380, for example using control signal CTRL_AT2. DigitalSubsystem 380 may be configured to vary the attenuation level of RFVariable Attenuator2 342 in order perform initial interferencecancellation processing of the combined jammer and SOI signal. Thevariably attenuated jammer and SOI signal may then be send to RF Filter2326. RF Filter2 326 may include a fixed RF bandpass filter and/ortunable RF filter to process and filter the combined jammer and SOIsignal prior to processing in Optical Subsystem 350. The RFpre-processed combined jammer and SOI signal (e.g., RF_in2) may then besent to Optical Subsystem 350 for further interference cancellationprocessing.

Optical Subsystem 350 may receive the RF pre-processed jammer signal(e.g., RF_in1) and the RF pre-processed combined jammer and SOI signal(e.g., RF_in2), may convert the signals from the RF domain to theoptical domain, and may perform further interference processing (e.g.,variable attenuation and/or inserting variable time delays) prior tocombining the optically converted signals to achieve interferencecancellation (See e.g., FIG. 3B). The resultant signal representing theSOI may be converted back to the RF domain and sent to RF SignalProcessor 374 (e.g., signal Op_out). Op_out may represent any residualinterference signal(s) present at the photodiode detector output (e.g.,if the interferer signal was not completely cancelled) and the SOI, andOp_out may be sent to RF Signal Processor 374. The SOI and the residualjammer signal at the output of Optical Subsystem 350 (e.g., Op_out) maybe processed and filtered by RF Signal Processor 374 prior to being sentto one or more of RF Correlator/Detector 338 (e.g., an RF Power Meter)and/or Transmit/Receive Switch2 348.

RF Signal Processor 374 may include one or more of fixed RF filters),low noise amplifier(s) (LNA(s)), fixed attenuator(s), variableatteuator(s), coupler(s), isolator(s), and/or other RF processingcomponents, for example depending on the application of the ICS. RFSignal Processor 374 may be configured to process the output of OpticalSubsystem 350 with minimal effect on the SOI. For example, when OpticalSubsystem 350 acts to cancel the interferer signal to obtain a cleanversion of the SOI, Optical Subsystem may introduce noise and/orattenuate the signal of interest during the interference cancellationprocess. In order to provide additional gain to the SOI aftercancellation, RF Signal Processor 374 may be applied to the output ofOptical Subsystem 350. For example, RF Signal Processor 374 may utilizeLNA2 328 to increase the power level of the SOI without furtheraccentuating the noise that may have been introduced to the signal. Inan example, RF Signal Processor 374 (e.g., and/or one or more of thereceive RF front-end components or the jammer RF front-end components)may be configured to be linear devices in order to avoid introducingdistortion to the signal of interest.

After processing by LNA2 328, the signal representing the SOI plus anyresidual interference may be sent to Rf Variable Attenuator3 330. RFVariable Attenuator3 330 may be a variable attenuator controlled byDigital Subsystem 380, for example using control signal CTRL_AT3.Digital Subsystem 380 may variably attenuate the signal representing theSOI plus any residual interference using RF Variable Attenuator3 330,for example to determine when Radio Transceiver 308 is operating intransmit mode. The variably attenuated signal representing the SOI plusany residual interference may then be filtered by RF Filter3 334 tofurther remove one or more noise components that may have been introduceby optical Subsystem 350. The signal representing the SOI plus anyresidual interference may then be sent to Coupler3 334, which may send acopy of the signal to each of RF Correlator/Detector 338 and/orIsolator2 336. Isolator2 336 may isolate the RF signal (e.g., preventreflection, etc.), and send a copy of the signal to Transmit/ReceiveSwitch 348. Depending on the configuration and/or current mode ofoperation of the ICS, the signal (which may represent the SOI if most orall of the interferer signal was successfully cancelled) may be pausedto Radio Transceiver 308 for further processing.

RF Signal Processor 374 may send the filtered SOI and residualinterference signal to RF Correlator/Detector 338. RFCorrelator/Detector 338 may send an RF correlator output signal (e.g.,RSSI_Rx) to Digital Subsystem 380. The RF correlator output signal maybe used by Digital Subsystem 380 to control the amplitude of one or morevariable attenuators (e.g., RF variable attenuators and/or opticalvariable attenuators of Optical Subsystem 350) and/or time delay and/orphase of variable time delay units. The signal RSSI_Rx may be a receivedsignal strength indication (RSSI) of any resultant interference signalas detected by the RF Correlator/Detector (e.g., plus the SOI). Forexample, the signal RSSI_Rx may be considered a measure of thecancellation depth of the ICS. For example, when RSSI_Rx is minimized,the cancellation depth of the ICS may be considered to be maximized(e.g., the cancellation of the jammer signal may be maximized). WhenRSSI_Rx is high or maximized, the cancellation depth of the ICS may beconsidered to be minimal (e.g., the jammer signal may be essentiallyuncancelled). Thus, the signal RSSI_Rx may be considered a measure ofthe dynamic range of the ICS.

In an example, RF Correlator/Detector 338 may include one or more mixerswith integrated synthesizers, fixed RF attenuators, bandpass filters,and/or LogAmps. The output signal RSSI_Rx may be measured continuallyduring cancellation to determine the residual content of the cancelledjammer signal. If the signal RSSI_Rx is minimized. Digital Subsystem 380may determine that the cancellation of the jammer has been maximized.When a cancellation threshold for RSSI_Rx is detected by DigitalSubsystem 380 (e.g., the power level of RSSI_Rx falls below athreshold). Digital Subsystem 380 may control Transmit/Receive Switch2to send the clean SOI signal to Radio Transceiver 308 for signalprocessing and reception.

Digital Subsystem 380 may be configured to implement a control loop thatutilizes the output of RF Correlator/Detector 338 as feedback fordetermining appropriate value for the attenuator gains and/or timedelays of Optical Subsystem 350 and/or for the attenuation gains of oneof more RF variable attenuators. These parameters may be stepped and/orvaried in order to minimize RF Correlator-Detector 338 output.Additionally, changes in RF Correlator/Detector 338 RSSI output levelsdetected in response to changes in attenuation and/or time delay may beused as feedback rather than or in addition to the overall magnitude ofthe RF Correlator/Detector 338 RSSI output. Since the SOI may beassociated with power levels that are orders of magnitude smaller thanthat of the jammer signal (e.g., Jammer 302 may operate on the order of+50 dBm (e.g., −5 dBm per 25 kHz channel) while the SOI may be on theorder of −60 dBm or lower. Since RF Correlator/Detector 338 output maybe considered a measure of RF power at the frequency of the SOI,reductions in the power level of RF Correlator/Detector 338 output maybe mainly due to the cancellation of the jammer signal from the combinedjammer plus SOI signal. DC offsets, if present in the control loop, mayhave little to no effect on the cancellation efficiency (e.g., do notreduce the cancellation efficiency) because, the DC offset may beconstantly added to RF Correlator/Detector 338 output value and hencemay not affect the difference in power levels utilized by the controlloop during ICS operation. These DC offsets may be due to electroniccomponent DC offsets as well as background noise presence in the RFsignal at the input of the power meter. The interference cancellationattenuation may be a function of the power meter dynamic range and/orSOI bandwidth.

Although the ICS interfaces with Radio Transceiver 308 that is used totransmit and/or receive SOIs, the transmit output power and transmitfrequency of Radio Transceiver 308 may be unknown to the ICS. Forexample, the ICS may be configured to be attached to wide range of radiotypes (e.g., utilizing different frequencies and/or bandwidths), andthus the ICS may be configured to determine the frequency of operationfor a given Radio Transceiver 308 and/or to determine when RadioTransceiver 308 is in transmitting mode. In an example, the componentsof RF Subsystem 310 may be configured to automatically detect thetransmit output power and frequency of Radio Transceiver 308. Forexample, Transmit Power Level Detector 342 may be configured to measurethe transmit power of Radio Transceiver 308.

One or more of Transmit/Receive Switch1 346 and/or Transmit/ReceiveSwitch2 348 may be controlled by Digital Subsystem 380 based on whetherRadio Transceiver 308 is in transmit mode or receive mode. For example,when Radio Transceiver 308 begins to transmit (e.g., as detected byTransmit Power Level Detector 342), the signal to be transmitted may besent from Radio Transceiver 308 to Transmit Coupler 376. TransmitCoupler 376 may send the signal to be transmitted to Transmit/ReceiveSwitch2 348. Since Radio Transceiver 308 is in transmit mode, DigitalSubsystem 380 may control Transmit/Receive Switch2 348 to send thetransmit signal to Transmit/Receive Switch1 346. Since Radio Transceiver308 is in transmit mode, Digital Subsystem 380 may controlTransmit/Receive Switch1 346 to send the transmit signal to Antenna2 306for transmission.

When Digital Subsystem 380 determines Radio Transceiver 308 is inreceive mode (e.g., based on signals received from Transmit Power LevelDetector 342), Digital Subsystem 380 may control the transmit/receiveswitches (e.g., Transmit/Receive Switch1 346 and/or Transmit/ReceiveSwitch2 348) based on whether Jammer 302 is currently in operation. Forexample, if Radio Transceiver 308 is in receive mode (e.g., determinedbased on Transmit Power Level Detector 342 output) and Jammer 302 is on(e.g., determined based on Jammer Detector 344 output), DigitalSubsystem 380 may control Transmit/Receive Switch1 346 to send thesignal received via Antenna2 306 to receive RF front-end components forinterference cancellation processing and may control Transmit/ReceiveSwitch2 348 to send the output of RF signal Processor 374 to TransmitCoupler 376 for processing by Radio Transceiver 308. If RadioTransceiver 308 is in receive mode (e.g., determined baaed on TransmitPower Level Detector 342 output) and Jammer 302 is off (e.g., determinedbased on Jammer Detector 344 output). Digital Subsystem 380 may controlTransmit/Receive Switch1 346 to send the signal received via Antenna2306 directly to Transmit/Receive Switch2 348. Digital Subsystem 348 maythen control Transmit/Receive Switch2 348 to send the output of RFsignal Processor 374 to Transmit Coupler 376 for processing by RadioTransceiver 308.

In order to determine whether Radio Transceiver is transmitting and/orthe frequency of operation of Radio Transceiver 308, Transmit Coupler376 may send a copy of the signals to be transmitted to RF Splitter 378.RF Splitter 378 may split the transmission signal and forward the signalto RF Frequency Detector 340 and Transmit Power Detector 342.

RF Frequency Detector 340 may be configured to measure the received RFsignal and/or a RF signal to be transmitted in order to determine thefrequency of the signal. RF Frequency Detector 340 may include one ormore mixer(s) with integrated synthesizer(s), fixed RF attenuators),bandpass filter(s), and/or LogAmp(s). RF Frequency Detector 340 may beconfigured to automatically detect the frequency by fast tuning of thesynthesizers for a known, fixed frequency, which may be referred to asan IF frequency (e.g., an example IF fixed frequency may be 70 MHz).When a maximum output power is measured at the output of the LogAmp byDigital Subsystem 380, input frequency to RF Frequency Detector 340 maybe determined by Digital Subsystem 380 based on knowledge of the known,fixed IF frequency and the current tuning levels of the localoscillators (e.g., components of the synthesizers).

The RSSI_TX signal may be received by Digital Subsystem 380 from RFFrequency Detector 340, and Digital Subsystem 380 may determine thefrequency of the input of RF Frequency Detector 340 based on RSSI_TX andthe tuning levels of the synthesizers. Transmit Power Level Detector 342may be configured to automatically determine the transmission power of asignal being transmitted via Antenna2 306. Transmit Power Level Detector342 may include one or more variable attenuator(s), an RF powerdetector(s), and/or comparator(s). The signals TX_ON and RSSI_TX may beutilized by Digital Subsystem 380 to determine parameters associatedwith Radio Transceiver 308 (e.g., power level and/or frequency) used fortransmitting via Antenna2 306. If the transmit and receive frequenciesare the same for Radio Transceiver 308, the knowledge of the transmitfrequency may be used to effectively cancel the jammer at thatfrequency.

FIG. 3D is a block diagram illustrating example components and examplesignals associated with Digital Subsystem 380. For example, DigitalSubsystem 380 may include one or more field programmable gate array(FPGA)-Digital Signal Processing (DSP) circuits with a plurality ofinput and/or output (I/O) interfaces (e.g., DSP & Interface Subsystem384). DSP & Interface Subsystem 384 may be an integrated circuit thatmay be configured to send and/or receive control signals in order toimplement one or more of the methods and techniques described herein.For example, DSP & Interface Subsystem 384 may be configured to sendand/or receive control signals to/from Optical Subsystem 350 and/or RFSubsystem 310. DSP & Interface Subsystem 384 may be implemented on aFPGA to implement control logic.

DSP & Interface Subsystem 384 may include Single Board Computer 382.Single Board Computer 382 may include a processor and/or memory. Forexample, Single Board Computer 382 may be configured to implement one ormore of the methods and/or techniques described herein. For example, thememory of the Single Board Computer 382 may include processor readableinstructions. The processor readable instructions may be executed by theprocessor in order to carry out one or more of the control methodsdescribed herein. For example, the control methods may include controlof one or more RF components of the RF subsystem, control of one or moreof the optical components of the optical subsystem, and/or control ofcomponents within Digital Subsystem 380 (e.g., DSP & Interface Subsystem384). The memory of the Single Board Computer 382 may include anytangible and/or physical memory such as random access memory (RAM),read-only memory (ROM), volatile memory, and/or non-volatile memory. Forexample, the computer readable instructions may be loaded into RAM inthe Single Board Computer and the instructions may be executed by theprocessor in order to perform one or more of the functions and/ormethods described herein.

In an example, Digital Subsystem 380 may be configured to convert thesignal RSSI_Rx from RF Subsystem 310 from the analog domain to digitaldomain, for example using an analog-to-digital converter (e.g., ADC1390). Similarly, Digital Subsystem 380 may be configured to convert thesignal RSSI_Tx from LogAmp2 442 of the RF Subsystem from the analogdomain to digital domain, for example using an analog-to-digitalconverter (e.g., ADC2 388). In an example, the digital control signalfor one or more of the optical attenuators included in Optical Subsystem350 may be controlled by Digital Subsystem 380 using control signalCTRL_OAT1. Digital-to-analog converter (DAC) 386 may be utilized inorder to control one or more optical attenuators of Optical Subsystem350. The control signal CTRL_OAT1 may be generated by Single BoardComputer 382 for the control of one or more optical delay lines ofOptical Subsystem 350. As may be appreciated, although a single controlsignal for the attenuators of the optical weighting network of OpticalSubsystem 350 is shown in FIG. 3D (e.g., CTRL_OAT1), more than onecontrol signal may be used, for example to control the one or moreoptical attenuators. For example, CTRL_OAT1 may include the signal a_c1,a_c2, . . . , a_cN etc. Similarly, although a single control signal forthe delay lines of the optical weighting network of Optical Subsystem350 is shown in FIG. 3D (e.g., CTRL_ODL1), more than one control signalmay be used, for example to control the one or more optical delay lines.For example, CTRL_ODL1 may include the signals t_c1, t_c2, . . . , t_cNetc.

The determination of when to begin or stop cancellation may be based onwhether the jammer is currently in operation. For example, DigitalSubsystem 380 may be configured to receive the signal JMR_ON from the RFSubsystem. The frequency of operation of the transceiver may bedetermined and/or measured by the Digital Control Subsystem. Forexample, the frequency of operation of the transceiver may be determinedand/or measured by the Digital Subsystem based on the signal TX_ON,which may be received from the RF Subsystem.

Digital Subsystem 380 may be configured to send the control signalsCTRL_SW1 and CTRL_SW2, for example to control Transmit/Receive BypassSwitch 1 and Transmit/Receive Bypass Switch 2, respectively. DigitalSubsystem 380 may be configured to control the fast tuning of the firstlocal oscillator (e.g., LO1/VCO1 426), for example using control signalCTRL_LO1. Digital Subsystem 380 may be configured to control the fasttuning of the second local oscillator (e.g., LO2/VCO2 428), for exampleusing control signal CTRL_LO2.

Digital Subsystem 380 may be configured to control one or more ofattenuation levels of various RF and/or optical attenuators. Forexample, Digital Subsystem 380 may be configured to control Variable RFAttenuator1 318 in the Jammer RF Front-End component of the RFSubsystem, for example by sending signal CTRL_AT1 to Variable RFAttenuator1 318. Digital Subsystem 380 may be configured to controlVariable RF Attenuator2 324 in the Receive RF Front-End component of theRF Subsystem, for example by sending signal CTRL_AT2 to Variable RFAttenuator2 324. Digital Subsystem 380 may be configured to controlVariable Attenuator3 in the RF Signal Processor component of the RFSubsystem (e.g., Variable Attenuator of Transmit Power Level Detector342), for example by sending signal CTRL_AT3 to Variable Attenuator 3.Digital Subsystem 380 may be configured to control Variable Attenuator 4in the Transmit Power Level Detector of the RF Subsystem, for example bysending signal CTRL_AT4 to Variable Attenuator 4.

FIG. 4 is a diagram that depicts an example architecture for cancellinginterference received in one or more radio signals. The architecture maybe implemented using a combination of electronic hardware and signalprocessing and control. One or more portions of the architecturedepicted in FIG. 4 may be implemented at a receiving device that mayreceive one or more SOIs via a communications network. The receivingdevice may also receive one or more signals that may cause interferencewith the one or more SOIs. One or more portions of the architecturedepicted in FIG. 4 may be implemented to cancel the interference, suchthat the receiving device may properly provide the one or more SOIs toan end user of the receiving device.

As shown in FIG. 4, one or more radios 416 a, 416 b, 416 c, 416 d may beconfigured to transmit and/or receive RF signals. The signals may betransmitted and/or received via one or more of antennas 404 a, 404 b,404 c, 404 d. The signals may be transmitted from and/or received at thecorresponding radio 416 a, 416 b, 416 c, 416 d via a transmit/receiveunit 408, a signal processor 426, and/or a transmit/receive unit 422.Signals being transmitted from one or more of the radios 416 a, 416 b,416 c, 416 d may bypass the signal processor 426, as the signalprocessor 426 may be used for processing incoming signals. Thetransmit/receive units 408, 422 may include a transmitter, a receiver, atransceiver, and/or any other device capable of transmitting and/orreceiving RF signals.

The transmit/receive unit 408 may include an RF receive tunablefront-end and transmit/receive switch. The RF receive tunable front-endmay include a low noise amplifier to increase the gain of incoming oroutgoing signals. The RF receive tunable front-end may include a tunableattenuator for varying the power level of the incoming and/or outgoingsignals. A tunable RF bandpas/lowpass/bandstop filter may be included inthe RF receive tunable front-end that may separate the transmittedand/or received SOI from harmonics and/or intermods. The RF receivetunable front-end may include an RF equalizer circuit for correction ofnon-linear portions of the amplitude and/or phase of the incomingsignals. The transmit/receive switch may direct any incoming or outgoingsignal to a corresponding transmit path or receive path of the ICS or tothe same corresponding paths of any subsystem connected to the ICS, suchas the radios 416 a, 416 b, 416 c and 416 d in FIG. 4.

The transmit/receive unit 422 may include a tunable RF band-pass filter(BPF) and transmit/receive switch. The tunable RF band-pass Filter (BPF)isolates the transmitted or received signal(s) from unwanted harmonicsand intermods, which may affect the expected quality of the SOI. Thetransmit/receive switch directs the incoming or outgoing signal to thecorresponding transmit path or receive path for each radio. The tunableRF BPF may isolate the transmitted and/or received signal(s) fromunwanted harmonics and/or intermods, which may affect the expectedquality of the SOI. The transmit/receive switch may direct the incomingor outgoing signal to the corresponding transmit path or receive pathfor each radio.

Each radio 416 a, 416 b, 416 c, 416 d may use a respective antenna 404a, 404 b, 404 c, 404 d to transmit and/or receive signals. Each radio416 a, 416 b, 416 c, 416 d may transmit and/or receive on a differentfrequency or frequency band. The signals may include data to be providedto an end user. The data may include audio data, text, picture data,video data, or any other data that may be communicated to an end uservia RF signals. The data may be communicated to one or more radios 416a, 416 b, 416 c, 416 d from the one or more sources via a signal whichmay be referred to as an SOI. The SOI received at antennas 404 a, 404 b,404 c, 404 d may be indicated by SOI2, SOI4, SOI6, SOI8, respectively.While the example illustrated in FIG. 4 shows four receiving radios 416a, 416 b, 416 c, 416 d, any number of receiving radios may beimplemented.

One or more of radios 414 a, 414 b, 414 c, 414 d may transmit respectiveinterfering signals I1, I3, I5, I7 that may interfere with one or moreof the SOI2, SOI4, SOI6, SOI8 being sent to the one or more radios 416a, 416 b, 416 c, 416 d. For example, the radios 414 a, 414 b, 414 c, 414d may be jammers that may attempt to jam signals being transmitted onone or more frequencies. The interfering signals I1, I3, I5, I7 may betransmitted to disrupt other forms of communication, but mayunintentionally disrupt one or more of the SOI2, SOI4, SOI6, SOI8. Forexample, the interference signals I1, I3, I5, I7 may be high power,broad band signals that may be transmitted to block or interfere withsignals being transmitted from a remote source (not shown). The signalstransmitted from the remote source may include hostile enemycommunications that may be sent to detonation devices, such as mines orIEDs, or other devices that may receive enemy communication signals.

The interfering signals I1, I3, I5, I7 may be transmitted from theradios 414 a, 414 b, 414 c, 414 d via a transmit/receive unit 420,interference couplers 418 a, 418 b, 418 c, 418 d, a transmit/receiveunit 410, and/or antennas 406 a, 406 b, 406 c, 406 d. Thetransmit/receive units 410, 420 may include a transmitter, a receiver, atransceiver, and/or any other device capable of transmitting and/orreceiving RF signals. The transmit/receive units 410, 420 may include aBPF tunable RF BPF and transmit/receive switch. The tunable RF BPF mayisolate the desired signal from unwanted signals in the communicationssystem, while the transmit/receive switch may direct incoming oroutgoing signals to the corresponding transmit path or receive path forthe radios connected to the ICS. Each interfering radio 414 a, 414 b,414 c, 414 d may use a respective antenna 406 a, 406 b, 406 c, 406 d fortransmission of interference. Each radio 414 a, 414 b, 414 c, 414 d maytransmit on a different frequency or frequency band. While the exampleillustrated in FIG. 4 shows four interfering radios 414 a, 414 b, 414 c,414 d, any number of interfering radios and/or receiving radios may beimplemented.

The signals received at each antenna 404 a, 404 b, 404 c, 404 d mayinclude an SOI, such as SOI2, SOI4, SOI6, or SOI8, and/or one or moreinterfering signals, such as I1, I3, I5, I7, which may be transmitted onone or more frequencies. The interfering signal I1 from radio 414 a maybe transmitted on frequency f1. The interfering signal I3 from radio 414b may be transmitted on frequency f3. The interfering signal I5 fromradio 414 c may be transmitted on frequency f5. The interfering signalI7 from radio 414 d may be transmitted on frequency f7. The SOI2directed to radio 416 a may be transmitted on frequency f2. The SOI4directed to radio 416 b may be transmitted on frequency f4. The SOI6directed to radio 416 c may be transmitted on frequency f6. The SOI8directed to radio 416 d may be transmitted on frequency f8.

A control unit 412 may control the allocated frequency spectrum for thecommunications equipment. The control unit 412 may allocate thefrequencies to radios 414 a, 414 b, 414 c, 414 d and/or radios 416 a,416 b, 416 c, 416 d. The frequencies may be allocated within theinstantaneous bandwidth of ˜100 MHz or higher. The control unit 412 mayallocate frequencies f1, f3, f5, f7 to radios 414 a, 414 b, 414 c, 414d, respectively. The frequencies may be increased for each radio, suchas where f1<f3<f5<f7 for example. The control unit 412 may allocatefrequencies f2, f4, f6, f8 to radios 416 a, 416 b, 416 c, 416 d,respectively. The frequencies may be increased for each radio, such aswhere f2<f4<f6<f8 for example. The frequencies f1, f3, f5, f7 may beless than or equal to the frequencies f2, f4, f6, f8, such as wheref1≦f2, f3≦f4, f5≦f6, and f7≦f8 for example.

The control unit 412 may provide control of one or more modules orfunctions in the communications system. For example, the control unitmay communicate with and/or control the radios 414 a, 414 b, 414 c, 414d, the radios 416 a, 416 b, 416 c, 416 d, the transmit/receive units408, 410, 420, 422, an ICS 402, the signal processor 426, an RF lifter424, and/or a power supply 430. The control unit 412 may include ageneral purpose processor, a special purpose processor, a conventionalprocessor, a digital signal processor (DSP), one or moremicroprocessors, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGA)circuits, any other type of integrated circuit (IC), and/or the like.The control unit 412 may be implemented in the field, in the air, onnaval ships, submarines, or in any other area in which wirelesscommunications equipment may be implemented.

The control unit 412 may receive an indication (e.g., INTERF_ON) fromthe transmit/receive unit 420 that may indicate whether interference maybe transmitted from one or more of the radios 414 a, 414 b, 414 c, 414d. The indication may be a bit indicator that may indicate that theinterference may be transmitted using one bit (e.g., ‘0’ or ‘1’) and mayindicate that interference may not be transmitted using another bit(e.g., ‘0’ or ‘1’). Upon receiving the indication, the control unit 412may control one or more other modules within the system, such as the ICS402, the RF filter 424, and/or the signal processor 426, to performinterference cancellation. The use of the ICS 402 may remain dormantuntil the control unit 412 detects interference from one or more of theradios 414 a, 414 b, 414 c, 414 d. Upon the detection of theinterference from one or more of the radios 414 a, 414 b, 414 c, 414 d,the control unit 412 may power on the ICS 402 and/or provideinstructions to the ICS 402 for filtering the interference from receivedsignals. The use of the ICS 402 may be controlled to conserve resources,such as the power provided by the power supply 430.

The interference received at the transmit/receive unit 408 may becancelled using the ICS 402. The ICS 402 may be a wideband optical ICS402 that may convert RF and/or digital signals to optical signals forinterference cancellation. While the ICS 402 may be described as anoptical ICS, the ICS 402 may perform interference cancellation usingother types of signals.

The ICS 402 may perform cancellation of the interfering signals I1, I3,I5, I7 based on samples of the interfering signals I1, I3, I5, I7. Thesamples of the interfering signals I1, I3, I5, I7 may be taken by theinterference couplers 418 a, 418 b, 418 c, 418 d. Each interferencecoupler 418 a, 418 b, 418 c, 418 d may take a sample from theinterference transmitted by a respective interferer radio 414 a, 414 b,414 c, 414 d. Interference couplers 418 a, 418 b, 418 c, 418 d may be RFfront-end interference couplers for the radios 414 a, 414 b, 414 c, 414d. The interference couplers may send the sample to the ICS 402 for usein interference cancellation. The ICS 402 may determine that one or moreof the interferers I1, I3, I5, I7 arc causing the interference in thesignal conprising one or more of the SOI2, SOI4, SOI6, SOI8 using theinterference samples from the one or more of the couplers 418 a, 418 b,418 c, 418 d. Once one or more of the interfering signals I1, I3, I5, I7are determined, the ICS 402 may use the samples from the one or moreinterfering signals I1, I3, I5, I7 to cancel the interference.

The ICS 402 may access interference information for the interferencesignals I1, I3, I5, I7 from a local or a remote source. In a co-locatedcommunications system, the radios 414 a, 414 b, 414 c, 414 d that may bethe source of the interference signals I1, I3, I5, I7 may be locatedwithin the same system as the radios 416 a, 416 b, 416 c, 416 d to whichSOIs may be directed. The optical ICS 402 may access the interferenceinformation for the interference signals I1, I3, I5, I7 remotely, fromone or more sources that may have knowledge of the interferenceinformation and may not be co-located with the radios 416 a, 416 b, 416c, 416 d. Where the interference radios 414 a, 414 b, 414 c, 414 d thatmay be the source of the interference signals I1, I3, I5, I7 are locatedin a remote location, the interference information may be unknown to theICS 402. When the interference information is unknown, the interferencemay be estimated, as described in U.S. Patent Application No. [AttorneyDocket No. LTEL_RI_US01], filed May 21, 2013.

Each of the interfering signals I1, I3, I5, I7 may be combined with oneor more of SOI2, SOI4, SOI6, SOI8 from a remote source when received atthe transmit/receive unit 408. The transmit/receive unit 408 may providethe signals to the ICS 402 for interference cancellation. The signalsmay include one or more of the SOI2, SOI4, SOI6, SOI8 and one or more ofthe interference signals I1, I3, I5, I7. In another example, thetransmit/receive unit 408 may provide the power levels of the signals tothe optical ICS 402 for cancellation. The transmit/receive unit 408 maybe made up of tunable attenuators very low noise amplifiers (LNAs) toprovide one or more of the SOI2, SOI4, SOI6, SOI8 and the interferencesignals I1, I3, I5, I7 levels to the optical ICS 402 for cancellation.

The optical ICS 402 may remove one or more of the interference signalsI1, I3, I5, I7 based on the received sampling of the interferencesignals I1, I3, I5, I7. For example, the optical ICS 402 may remove theinterference signals I1, I3, I5, I7 over a wide and instantaneousbandwidth (e.g., 150 MHz). The interference may be removed withoutappreciably degrading the SOI2, SOI4, SOI6, SOI8.

The ICS 402 may use optical signals to cancel the interference signalsI1, I3, I5, I7. The ICS 402 may include an optical transmission modulethat may convert the interference signals I1, I3, I5, I7 and/or theSOI2, SOI4, SOI6, SOI8 from RF signals to optical signals. The opticaltransmission module may include a laser modulator for converting the RFsignal to optical signals. The optical transmission module may invertthe sample of the one or more of the interference signals I1, I3, I5,I7. The signals received from the transmit/receive unit 408 may eachinclude an SOI2, SOI4, SOI6, SOI8 and one or more of the interferencesignals I1, I3, I5, I7. The inverted optical interference signals I1,I3, I5, I7 may be combined with the optical signals that include the SOIand one or more of the interference signals interference signal signalsI1, I3, I5, I7. The inverted interference signals I1, I3, I5, I7 maycancel the interference from the signals having the SOI.

The interference from one or more of radios 414 a, 414 b, 414 c, 414 dmay be cancelled using one or more optical paths. An optical path mayinclude an instantaneous bandwidth of over 150 MHz. One or more of theinterfering signals I1, I3, I5, I7 may be combined into a single opticalinterference signal for interference cancellation. The combinedinterfering signals may be used to cancel each interfering signal fromthe signals received at the transmit/receive unit 408. To further cancelone or more other interfering signals I1, I3, I5, I7, or one or moreinterfering signals I1, I3, I5, I7 received at another time period,additional multipath components may be implemented at the ICS 402. Forexample, a second and/or a third multipath component, as shown in FIG. 3for example, may be implemented to perform additional interferencecancellation.

The interference from one or more of radios 414 a, 414 b, 414 c, 414 dmay be cancelled using a single optical path. The ICS 402 may determinea level of interference from the samples of multiple interferencesignals I1, I3, I5, I7. Multiple interference signals I1, I3, I5, I7 maybe combined for cancellation. One or more of the signals received fromthe transmit/receive unit 408 that include the SOI2, SOI4, SOI6, and/orSOI8 may be combined. The combined interference signals I1, I3, I5,and/or I7 may be inverted and combined with the signals received fromthe transmit/receive unit 408. The signal that includes the multipleinverted interference signals I1, I3, I5, and/or I7 may cancel theinterference of the signals received from the transmit/receive unit 408.Using the combined interference signal, the interference from multipleradios 414 a, 414 b, 414 c, 414 d may be negated with a single opticalsignal and/or a single optical path.

The signals received at the ICS 402 from the transmit/receive unit 408may be received by the ICS 402 at a different time or frequency than thesamples of the interfering signals I1, I3, I5, I7. For example, thesignals received at the ICS 402 from the transmit/receive unit 408 maybe received over the air and may be received later in time than theinterfering signals I1, I3, I5, I7, which may be received via a wirelineconnection. Variable optical delays may be used in the ICS 402 to causedelays in received signals for interference cancellation. The delay mayallow the interfering signals I1, I3, I5, I7 to align with the signalsreceived from the transmit/receive unit 408 for cancellation. A lengthof optical cable in the ICS 402 may provide the sample of theinterfering signals I1, I3, I5, I7 to a tapped delay line with a delaythat is close to the antenna coupling delay. The length of the delay maybe used to minimize dispersion for broadband cancellation and/or provideRF isolation. Variable optical attenuators may be used in the opticalICS 402 to achieve an RF power level for interference cancellation. TheLaser Modulator 1 and 2 in FIG. 3 may provide the phase shift to allowthe interfering signals I1, I3, I5, I7 to align with the signalsreceived from the transmit/receive unit 408 for cancellation.

The ICS 402 may convert the optical signal to an RF signal and may sendthe signal to the RF filter 424. The RF filter 424 may be a tunable RFfilter. The RF filter 424 may clean up the RF signals before they may besent to and/or processed by any other module in the system. The clean upby the RF filter 424 may prevent generation of harmonies and/orintermods within the system. The RF filter 424 may separate the SOI2,SOI4, SOI6, and/or SOI8. The RF filter 424 may provide isolation betweenone or more of the radios 416 a, 416 b, 416 c, 416 d by separating theSOI2, SOI4, SOI6, and/or SOI8 according to the frequency of thecorresponding radio 416 a, 416 b, 416 c, 416 d to which each SOI may bedirected.

The RF filter 424 may send one or more of the signals SOI2, SOI4, SOI6,SOI8 to a signal processor 426. The signal processor 426 may be an RFand/or digital signal processor for processing RF and/or digitalsignals. The received SOI2, SOI4, SOI6, SOI8 may have some residualinterference. The signal processor 426 may determine if the signal isclean enough for sending to the intended radio 416 a, 416 b, 416 c, 416d. The signal processor 426 may determine cleanliness of the SOI2, SOI4,SOI6, and/or SOI8 based on the signal to noise ratio (SNR). Theprocessor may determine whether the SNR for the SOI2, SOI4, SOI6, and/orSOI8 meets a threshold. The signal processor may be used to determinethe SNR by measuring a peak to average power spectrum density ratio,which may be used for the interference cancellation level indication forexample. The threshold may be a minimum level at which a user mayunderstand the SOI2, SOI4, SOI6, and/or SOI8, such as a 10 dB thresholdfor example. If the peak to average power spectrum density ratio doesnot meet the threshold for a SNR, then the signal processor 426 mayprevent the signal from being passed to the intended radio 416 a, 416 b,416 c, 416 d and/or may send the signal to the ICS 402 for furtherinterference cancellation. The signal processor may wait until thecancellation depth reaches a predetermined value to apply the signal tothe input of the radio transceiver.

The signal processor 426 may include an RF correlator 428 that may beused to detect the SOI2, SOI4, SOI6, SOI8, based on a sample forexample. The RF correlator 428 may determine whether the SNR between oneor more of the SOI2, SOI4, SOI6, SOI8 and one or more interferingsignals I1, I3, I5, I7 meets a threshold. If the SNR meets thethreshold, then the signal may be passed to the intended radio 416 a,416 b, 416 c, 416 d for reception. Any resultant interference signal maycause the RF correlator 428 to send an output at the signal processor,which may be used to control amplitude and/or phase of the weightingnetworks made up of variable optical attenuators and delay lines in theoptical ICS. The SNR may be determined based on a received signalstrength indication (RSSI) that may be measured by the RF correlator.The RSSI value may indicate that the measured signal may be sent to theICS 402 for additional interference cancellation and/or that the ICS 402may be tuned to improve interference cancellation. If the received RSSIvalue of the received signal is above the threshold, the signalprocessor 426 may determine that the signal includes interference. TheRF correlator 428 may measure the amount by which the received signalexceeds the threshold and may use this amount to tune the ICS 402 tomore accurately cancel the interference from the received signals.

If an SOI2, SOI4, SOI6, SOI8 is too low, an RF correlator 428 may beused to raise the SOI2, SOI4, SOI6, SOI8. For example, the SOI2, SOI4,SOI6, SOI8 may be raised to at least the threshold level. The signalprocessor 426 may prevent the signal from being passed to the intendedradio 416 a, 416 b, 416 c, 416 d until the SNR may be improved (e.g.,through further interference cancellation and/or increasing the SOI)such that it reaches the threshold.

The filtered signal may be returned to the ICS 402 one or more times foradditional signal cancellation to filter out residual interference. Thesignal may be processed by the ICS 402 a predetermined number of timesor until the SNR reaches a threshold. The signal processor 426 may sendthe filtered signal back to the ICS 402 if the SNR does not reach thethreshold. The signal processor 426 may send a received signal strengthindication (RSSI) to the control unit 412. The RF correlator may measurean amount of power of the received signal at the signal processor 426and may send the RSSI to the control unit 412. The control unit 412 maydetermine whether to continue to filter the signal based on the totalpower of the signal. If the total power of the signal is above athreshold, such as a power threshold at which data may be received, thesignal may include additional interference. The control unit 412 mayinstruct the signal processor to send the filtered signal to the ICS 402for further processing.

Table 1, illustrated below, comprises an example of the SNR for multipleinterfering signals and an SOI. In Table 1, Interferer 1 and Interferer2 are used as example interfering signals, but one or more interferingsignals may be used. The power level of Interferer 1 may be equal to thepower level of Interferer 2. The power level of Interferer 1 andInterferer 2 for the example shown in Table 1 may be 100 W. The powerlevel for the SOI may be 20 W. Interferer 1 and Interferer 2 may be twoof the interfering signals I1, I3, I5, I7. The SOI may be one of SOI2,SOI4, SOI6, SOI8. While two interfering signals are used in the examplein Table 1, the example illustrated in Table 1 may be implemented usingany number of interfering signals.

TABLE 1 SIGNAL-TO-NOISE RATIO FOR SOI AND TWO INTERFERERS (Interferer 1& Interferer 2) @ 300 MHz Interferer 1 Tx Interferer 1 Tx Interferer 1Interferer 2 Interferer 3 Tx Interferer 1 Path Power in Power in TxPower in Path Loss Power in Loss in dB 2.2 m BW = 150 MHz BW = 150 MHzBW = 25 kHz in dB 50 m BW = 150 MHz away @ in W −29 dB in dBm −29 dB indBm −29 dB away @ in W −56 dB 300 MHz Path Loss Path Loss Path Loss 300MHz Path Loss 29 0.13 21.00 −16.78 56.00 0.00025 Interferer 2 Interferer3 Tx SOI2 Rx Tx Power in Power in Power in SOI2 Rx Power BW = 150 MHz BW= 25 kHz in BW = 25 kHz in in BW = 25 kHz in dBm −56 dB dBm −56 dB W −56dB Path in dBm −56 dB Path Loss Path Loss Loss Path Loss −6.02 −43.800.00005 −13.01 SOI2 to SOI2 to Interferer 1 and SOI2 BW in Interferer 1Interferer 3 2 BW in kHz kHz SNR in dB SNR in dB 150000 25 3.77 30.79

As shown in Table 1, the SNR for the SOI and Interferer 1 may be below athreshold and the SNR for the SOI and Interferer 2 may be above athreshold. The threshold may be 10 dB, which may be a minimum level atwhich a user may understand the SOI. The SNR for the SOI and Interferer1 may be 3.77 dB. The SNR for the SOI and Interferer 2 may be 30.8 dB.The higher SNR for the SOI and Interferer 2 may be because the transmitpower of Interferer 2 may be spread over a larger bandwidth (e.g., 150MHz) compared to the bandwidth of the radio receiver (e.g., 25 kHz). Thetransmit power of Interferer 1 may be transmitted over the samebandwidth as Interferer 2 (e.g., 150 MHz), but the power level ofInterferer 1 (e.g., 21 dBm) may be higher than that of Interferer 2(e.g., −6.02 dBm). With the difference in power, the lower SNR for theSOI and Interferer 1 may not meet the predetermined threshold.

As illustrated by the example shown in Table 1, cancellation of aportion of the interfering signals may be enough to satisfy thepredetermined threshold. For example, since the SNR for the SOI andInterferer 2 may be higher than the predetermined threshold, theinterfering signal from Interferer 2 may not be cancelled by the opticalICS 402. As the SNR for the SOI and Interferer 1 may be lower than thepredetermined threshold, the interfering signal from Interferer 1 may becancelled by the optical ICS 402. The same determination may be made(e.g., at the optical ICS 402) for any number of interfering signals.The SNR may be determined for each interfering signal independently orin combination with other interfering signals.

FIG. 5 is a diagram that depicts an example architecture for an opticalICS 502 for one or more of interferers 506, 508, 510. An opticalcancellation path shown in ICS 502 may be used for one or more of thesignals received from the interferers 506, 508, 510. The interferers506, 508, 510 may transmit within a 150 MHz bandwidth. The optical ICS502 may include an ICS transmitter module (+) 512 configured to receivean SOI from the signal source 504 and interference signals from one ormore of the interferers 506, 508, 510. A sample of the RF signals fromone or more of the interferers 506, 508, 510 may be received at thetransmitter module (−) 514. Once the ICS 502 receives the RF signals itmay convert them to optical for cancellation of the interference. Thetransmitter module (−) 514 may change the interfering signals 180degrees to cancel out the one or more of the interfering signalsreceived at the transmitter module (+) 512.

A tunable delay 516 may be implemented to adjust the timing of signalsreceived at the ICS 502 for interference cancellation. The tunable delay516 may delay one or more interfering signals received at thetransmitter module (−) 514 so that they may be aligned in time with oneor more signals received at the transmitter module (+) 512. The signalsreceived at the transmitter module (+) 512, which may be received overthe air, may have a larger delay between transmission and receipt thanthe interfering signals received at the transmitter module (−) 514,which may be wired transmission that may be coupled directly to the ICS502. The tunable delay 516 may be used to balance out the distancebetween the two paths.

A tunable attenuator 518 may be implemented to adjust the signalstrength of one or more interfering signals for interferencecancellation. The tunable attenuator 518 may know signal strength atwhich one or more interfering signals may be received at the transmittermodule (+) 512. The tunable attenuator 518 may change the level of theinterfering signals received at the transmitter module (−) 514 so thatthe signal strength is the same, or similar, to the signal strength ofthe interference received at the transmitter module (+) 512.

While the ICS 502 may be depicted with a single optical cancellationpath, one or more optical cancellation paths may be implemented in theoptical ICS 502. Each optical cancellation path may include an opticaltransmitter module (−), a tunable delay, and/or a tunable attenuator.The number of optical cancellation paths may depend on the environmentin which the optical ICS 502 is implemented. For example, in anenvironment with buildings or other objects that may cause signal delay,multiple optical paths may be used to capture delayed signals. Theoptical ICS 502 may include an optical cancellation path per interferingsignal or group of interfering signals. The optical ICS 502 mayimplement each optical cancellation path based on a time period in whichone or more interfering signals may be received. For example, theinterfering signals from interferer 506 and interferer 508 may bereceived within a same time period and may be grouped together forprocessing via one optical cancellation path, while the interferingsignal from the interferer 510 may be received later in time and may beprocessed via another optical cancellation path. If the RSSI value ofone or more signals meets a threshold, multiple paths may be used.

After the interfering signals are processed by the tunable delay 516and/or tunable attenuator 518, the interfering signal may be cancelledat 524. The inverted interference signals may be combined with thesignals from the transmitter module (+) 512 to cancel the interference.A tapped delay line/weighting network summed output may be combined witha receiver antenna input through a laser modulator (−) for coherentcancellation of the interference signal. The SOI may be output to thephotodiode receiver after cancellation has been performed. Thephotodiode receiver 524 may transfer the SOI from optical to RF forbeing sent as output to a signal processor 522.

A tunable delay 516 and/or the tunable attenuator 518 may be adjusted toimprove the timing and/or signal strength of received signals. Thesignal processor 522 may perform measurements on the RSSI and thetunable delay 516 and/or the tunable attenuator 518 may be adjustedbased on the RSSI. The signal processor 522 may measure the residualsignal strength over which the RSSI value exceeds a threshold and maychange the delay to meet the threshold value.

The control loop may vary both gain and phase shift for power meteroutput, which may indicate an effectively cancelled interference signal.DC offset in the control group may not reduce the cancellationefficiency because, if present, it may be added to the power meteroutput value and may not affect the difference used for the controlgroup operation. These DC offsets may be due to electronic component DCoffsets and/or background noise presence in the RF signal at the inputof the power meter. The interference cancellation attenuation may be afunction of the power meter dynamic range and/or SOI bandwidth.

FIGS. 6 and 7 are graphs that illustrate the performance of the opticalICS for two interferers, Interferer 1 and Interferer 2, and threeinterferers, Interferer 1, Interferer 2, and Interferer 3, respectively.The spectral bandwidth of the signals in FIGS. 6 and 7 may be 150 MHz.The SNR is illustrated in as the difference between the SOI and theinterference signals shown in FIGS. 6 and 7.

FIG. 6 is a graph that illustrates the performance of the optical ICSfor two interferers, Interferer 1 and Interferer 2. As shown in FIG. 6,Interferer 1 and Interferer 2 may be received at about −56 dBm beforecancellation, which may be about the strength at which the SOI may bereceived. After cancellation, Interferer 1 and Interferer 2 may have asignal strength of about −94 dBm. This interference cancellation mayallow a user to properly receive the SOI. The cancellation attenuationmay be about 38 dB.

FIG. 7 is a graph that illustrates the performance of the optical ICSfor three interferers, Interferer 1, Interferer 2, and Interferer 3. Asshown in FIG. 7, Interferer 1, Interferer 2, and Interferer 3 may bereceived at about −53 dBm before cancellation, which may be about thestrength at which the SOI may be received. After cancellation,Interferer 1, Interferer 2, and Interferer 3 may have a signal strengthof about −93 dBm. The SNR after cancellation may be about 40 dB. Whilecancellation attenuation in FIGS. 6 and 7 may be between about 38 dB and40 dB, cancellation attenuation may be in excess of 45 dB in 150 MHzbandwidth.

Although features and elements are described above in particularcombinations, each feature or element can be used alone or in anycombination with the other features and elements. Though the featuresand elements may be implemented for handling co-site, narrowband, and/orwideband interference, they may be implemented on other programs. Inaddition, the methods described herein may be implemented in a computerprogram, software, or firmware incorporated in a computer-readablemedium for execution by a computer or processor. Examples ofcomputer-readable media include electronic signals transmitted overwired or wireless connections) and computer-readable storage media.Examples of computer-readable storage media include, but are not limitedto, a read only memory (ROM), a random access memory (RAM), a register,cache memory, semiconductor memory devices, magnetic media such asinternal hard disks and removable disks, magneto-optical media, andoptical media such as CD-ROM disks, and digital versatile disks (DVDs).A processor in association with software may be used to implement aradio frequency transceiver for use in a WTRU, terminal, base station,RNC, or any host computer.

What is claimed:
 1. An interference cancellation system (ICS), the ICScomprising: a processor configured to: receive a plurality ofinterference signals, receive a combined signal that includes acombination of the plurality of interference signals and a signal ofinterest (SOI), variably attenuate and variably time delay one or moreof the interference signal and the combined signal, convert theplurality of interference signals into at least one optical interferencesignal, convert the combined signal into an optical signal, and cancelat least one portion of the interference signal from the combined signalbased on the at least one optical interference signal.
 2. The ICS ofclaim 1, wherein the plurality of interference signals are convertedinto a single optical interference signal for cancellation.
 3. The ICSof claim 1, wherein the plurality of interference signals are eachconverted into a respective optical interference signal forcancellation.